/* Copyright (C) 2004 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */
/* $Id: hashtable.c 564 2008-08-01 16:59:25Z mtm $ */

#include "hashtable.h"
#include "hashtable_private.h"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*
Credit for primes table: Aaron Krowne
 http://br.endernet.org/~akrowne/
 http://planetmath.org/encyclopedia/GoodHashTablePrimes.html
*/
static const unsigned int primes[] = {
    53, 97, 193, 389, 769, 1543, 3079,
    6151, 12289, 24593, 49157, 98317, 196613, 393241,
    786433, 1572869, 3145739, 6291469, 12582917, 25165843, 50331653,
    100663319, 201326611, 402653189, 805306457, 1610612741
};
const size_t prime_table_length = sizeof(primes) / sizeof(primes[0]);
const float max_load_factor = 0.65;
/*****************************************************************************/
struct hashtable*
create_hashtable(unsigned int minsize,
    unsigned int (*hashf)(void*),
    int (*eqf)(void*, void*))
{
    struct hashtable* h;
    unsigned int pindex, size = primes[0];
    /* Check requested hashtable isn't too large */
    if (minsize > (1u << 30))
        return NULL;
    /* Enforce size as prime */
    for (pindex = 0; pindex < prime_table_length; pindex++) {
        if (primes[pindex] > minsize) {
            size = primes[pindex];
            break;
        }
    }
    h = (struct hashtable*)malloc(sizeof(*h));
    if (NULL == h)
        return NULL; /*oom*/
    h->table = (struct entry**)calloc(size, sizeof(*h->table));
    if (NULL == h->table) {
        free(h);
        return NULL;
    } /*oom*/
    h->tablelength = size;
    h->primeindex = pindex;
    h->entrycount = 0;
    h->hashfn = hashf;
    h->eqfn = eqf;
    h->loadlimit = (unsigned int)ceil(size * max_load_factor);
    return h;
}

/*****************************************************************************/
unsigned int
hash(struct hashtable* h, void* k)
{
    /* Aim to protect against poor hash functions by adding logic here
     * - logic taken from java 1.4 hashtable source */
    unsigned int i = h->hashfn(k);
#if 0
    i += ~(i << 9);
    i ^=  ((i >> 14) | (i << 18)); /* >>> */
    i +=  (i << 4);
    i ^=  ((i >> 10) | (i << 22)); /* >>> */
#endif
    return i;
}

/*****************************************************************************/
static int
hashtable_expand(struct hashtable* h)
{
    /* Double the size of the table to accomodate more entries */
    struct entry** newtable;
    struct entry* e;
    struct entry** pE;
    unsigned int newsize, i, hindex;
    /* Check we're not hitting max capacity */
    if (h->primeindex == (prime_table_length - 1))
        return 0;
    newsize = primes[++(h->primeindex)];

    newtable = (struct entry**)calloc(newsize, sizeof(*newtable));
    if (NULL != newtable) {
        /* This algorithm is not 'stable'. ie. it reverses the list
         * when it transfers entries between the tables */
        for (i = 0; i < h->tablelength; i++) {
            while (NULL != (e = h->table[i])) {
                h->table[i] = e->next;
                hindex = indexFor(newsize, e->h);
                e->next = newtable[hindex];
                newtable[hindex] = e;
            }
        }
        free(h->table);
        h->table = newtable;
    }
    /* Plan B: realloc instead */
    else {
        newtable = (struct entry**)realloc(h->table, newsize * sizeof(*newtable));
        if (NULL == newtable) {
            (h->primeindex)--;
            return 0;
        }
        h->table = newtable;
        memset(newtable[h->tablelength], 0, newsize - h->tablelength);
        for (i = 0; i < h->tablelength; i++) {
            for (pE = &(newtable[i]), e = *pE; e != NULL; e = *pE) {
                hindex = indexFor(newsize, e->h);
                if (hindex == i) {
                    pE = &(e->next);
                } else {
                    *pE = e->next;
                    e->next = newtable[hindex];
                    newtable[hindex] = e;
                }
            }
        }
    }
    h->tablelength = newsize;
    h->loadlimit = (unsigned int)ceil(newsize * max_load_factor);
    return -1;
}

/*****************************************************************************/
unsigned int
hashtable_count(struct hashtable* h)
{
    return h->entrycount;
}

/*****************************************************************************/
int hashtable_insert(struct hashtable* h, void* k, void* v)
{
    /* This method allows duplicate keys - but they shouldn't be used */
    unsigned int hindex;
    struct entry* e;
    if (++(h->entrycount) > h->loadlimit) {
        /* Ignore the return value. If expand fails, we should
         * still try cramming just this value into the existing table
         * -- we may not have memory for a larger table, but one more
         * element may be ok. Next time we insert, we'll try expanding again.*/
        hashtable_expand(h);
    }
    e = (struct entry*)malloc(sizeof(*e));
    if (NULL == e) {
        --(h->entrycount);
        return 0;
    } /*oom*/
    e->h = hash(h, k);
    hindex = indexFor(h->tablelength, e->h);
    e->k = k;
    e->v = v;
    e->next = h->table[hindex];
    h->table[hindex] = e;
    return -1;
}

/*****************************************************************************/
void* /* returns value associated with key */
hashtable_search(struct hashtable* h, void* k)
{
    struct entry* e;
    unsigned int hashvalue, hindex;
    hashvalue = hash(h, k);
    hindex = indexFor(h->tablelength, hashvalue);
    e = h->table[hindex];
    while (NULL != e) {
        /* Check hash value to short circuit heavier comparison */
        if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
            return e->v;
        e = e->next;
    }
    return NULL;
}

/*****************************************************************************/
void* /* returns value associated with key */
hashtable_remove(struct hashtable* h, void* k)
{
    /* TODO: consider compacting the table when the load factor drops enough,
     *       or provide a 'compact' method. */

    struct entry* e;
    struct entry** pE;
    void* v;
    unsigned int hashvalue, hindex;

    hashvalue = hash(h, k);
    hindex = indexFor(h->tablelength, hash(h, k));
    pE = &(h->table[hindex]);
    e = *pE;
    while (NULL != e) {
        /* Check hash value to short circuit heavier comparison */
        if ((hashvalue == e->h) && (h->eqfn(k, e->k))) {
            *pE = e->next;
            h->entrycount--;
            v = e->v;
            freekey(e->k);
            free(e);
            return v;
        }
        pE = &(e->next);
        e = e->next;
    }
    return NULL;
}

/*****************************************************************************/
/* destroy */
void hashtable_destroy(struct hashtable* h, int free_values)
{
    unsigned int i;
    struct entry *e, *f;
    struct entry** table = h->table;
    if (free_values) {
        for (i = 0; i < h->tablelength; i++) {
            e = table[i];
            while (NULL != e) {
                f = e;
                e = e->next;
                freekey(f->k);
                free(f->v);
                free(f);
            }
        }
    } else {
        for (i = 0; i < h->tablelength; i++) {
            e = table[i];
            while (NULL != e) {
                f = e;
                e = e->next;
                freekey(f->k);
                free(f);
            }
        }
    }
    free(h->table);
    free(h);
}

/*
 * Copyright (c) 2002, Christopher Clark
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of the original author; nor the names of any contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
